ALGAL AND FUNGAL PROTISTS 



51 



" manna " in case 



rocks and, scattered by winds, serves as 

 of need. This Lecanora when dry is said (A. Lorrain Smith) 

 to contain over 60 per cent, of crystals of oxalate of lime. 

 The real nature of lichens was first explained by Schwenender 

 in 1867, but it was many years before his view was accepted 

 in England. The word symbiosis was created by de Bary 



sp 



FIG. 12. SOME FEATURES OF PARASITIC FUNGI, a, Phytophthora infestans, 

 the zoospore, z, in germinating secretes a capsule which it leaves 

 and penetrates into an epidermal cell of a potato-plant ; b, end of a 

 hypha of Cystopus candidus with knob-shaped haustoria penetrating 

 into a cell of its host ; c, Peronospora calotheca with a branching 

 haustorium ; d, the beginning of the lichen Physcia parietina, sp, 

 spore of the fungus which has germinated, its hypha sending branches 

 round two cells of the alga, Protococcus viridis, p ; e, fungal hyphae 

 and Protococcus from the lichen Cladonia furcata. After de Bary. 



to express the relationship of the two participating organisms 

 or symbionts of lichens. 



Other examples of symbiosis are shown by the zoochlorels, 

 unicellular algae found in symbiosis with many fresh- 

 water protozoa and invertebrates ; and by the zooxanthels, 



